✍ Scribed by M. Decré; E. Gailly; J.-M. Buchlin
No coin nor oath required. For personal study only.
The ribbing instability hinders the roll coating process, as it produces w a y coating films, The technique studied here prevents ribbing, whereby a string is placed parallel to the rolls, in contact with the unstable meniscus. In this experiment, the fluid is a Newtonian oil. A free-surface visualization technique allows measurement of the interface profile where the string interacts with the forming films. The ribbing can be eliminated under conditions at least 20 times its natural onset. The influence of the string position on the mass transfer is then examined. Measurements show that the streamwise position of the string controls the total flow rate of the process, while its transverse position accurately controls the relative thicknesses applied on each roll. The string proves to be both an eficient concept to eliminate ribbing, and a reliable way of $king the coating film thickness, without resorting to traditional gap width and roller speeds selection. * !
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